Intragenic deletions of IL1RAPL1: Report of two cases and review of the literature.

IL1RAPL1 (interleukin-1 receptor accessory protein-like 1) located at Xp21.3-22.1 has repeatedly been shown to be deleted in patients with a contiguous gene syndrome also affecting neighboring genes, in particular DMD (dystrophin), DAX-1 (NR0B1, nuclear receptor subfamily 0, group B, member 1), and GK (glycerol kinase). In contrast, intragenic deletions of IL1RAPL1 or other mutations or cytogenetic aberrations affecting IL1RAPL1 have only rarely been identified. Up to date, they have mostly been associated with nonspecific mental retardation (MRX). We report on two nonrelated patients with MR and additional dysmorphic features who both show intragenic deletions of IL1RAPL1, one of them being de novo (exon 2) and the other one being inherited from his mother (exons 3-5). Deletions were identified by microarray-based chromosome analysis and confirmed by multiplex PCR and FISH, respectively. These data, along with recent functional studies indicating its role in neuronal development, provide further evidence for the relevance of IL1RAPL1 in the pathogenesis of X-linked MR and add knowledge to the phenotypic spectrum of IL1RAPL1 mutations.